In this issue of The Journal, Spitz et al1 examine child-bearing rates for US teenagers in the decade of the 1980s. The authors wisely divide these data into 5-year periods. To have done otherwise would have been misleading, for these rates prove to have been mercurial: stable from 1980 to 1985, markedly increased for 1985 to 1990. An analysis of more recent data shows rates declining in 1991 to 1992.2 Accordingly, before attributing meaning to these data, one must take a longer view. In the 1970s, birth rates among adolescents declined sharply, probably owing to the legalization and availability of abortion; for reasons that are not clear, these rates then leveled off until 1988, when they rose to a new peak for 10- to 17-year-olds.3(p334)

See also p 989.

Using as the denominator the numbers of sexually active adolescent girls rather than all those in a given